I'd like to have an easy way to declare an operator that brackets its argument with a particular delimiter. As an example I'd like to be able to write
to mean the same as
FYI I know how to do
but I thought I once saw a package that provided some command like
sort of a combination of
\DeclareMathOperator and I think it also defined a starred version of the operator that didn't take any argument and didn't produce the delimiters.